Overview of fire retardant mechanisms

Combustion and fire retardance in polymeric materials

“…Recent studies showed that the nature of such species depends on the competition between chemical halogenation of the metal oxide and thermal disproportionation of metal oxyhalides to metal halide and lower-halogen content oxyhalide (or metal oxide) [3]. The result of the competition varies with the temperature of the condensed phase during burning.…”

“…The result of the competition varies with the temperature of the condensed phase during burning. These data will be of basic importance in the study of the interactions between synergistic halogenated fire retardants and polymer matrix which is still in its early steps [3].…”

“…A most important parameter is the concentration of oxygen on the surface of the burning polymer and hence the occurrence of thermal oxidation in the condensed phase. This is a most controversial point which might be rationalised so far by assuming that it depends on the type of polymer and burning conditions [3].…”

“…The awareness of possible negative side effects in halogen-based fire retardants, has recently increased the interest for halogen-free systems, among which the intumescent ones seem to be most promising [3,6,71. A foamed multicellular char is formed by intumescent systems on heating which shields the underlying material from the action of the flame.…”

Synthesis and thermal analytical screening of metal complexes as potential novel fire retardants in polyamide 6.6

“…16,20 Neither ATO nor ZnS alone has any significant effect on the thermal degradation or flame retardant behaviour of most polymers, but in combination with an appropriate primary halogen-containing FR, a significant increase in performance is observed relative to a halogen-only control. 9,14,21 Both these synergists are understood to react with the hydrohalic acids (either HCl or HBr) produced by halogenated flame retardants during their thermal degradation to form volatile metal halides which serve to mediate the release of halogen radicals in the vapour phase. 9,14,21 For ATO, this processes is understood to take place via the gradual volatilisation of SbX3 (where X is Cl or Br) from a range of antimony oxyhalides, whereas for ZnS, the process is less well understood, as either Zn or Sn could potentially be released to the vapour phase in the form of Zn (II), Sn (IV) or Sn (II) chlorides or bromides.…”